With the advantages of high quality display, cheap, easily portable, liquid crystal display, is usually used in the mobile communications equipment, pc, TV . . . etc. Currently the liquid crystal display consists of an upper substrate, a down substrate, and a middle crystal layer, the substrates consist of the glass and the electrode. If there are electrodes both on the upper substrate and the down substrate, the vertical electric field type display is formed, for example, TN (Twist Nematic) type, VA (Vertical Alignment) type, and MVA (Multidomain Vertical Alignment) type for the wide viewing angle. Another type is different from the describe above, the electrode is on one side of the substrate to form the horizontal electric field type display, for example, IPS (In-plane-switching) type, FFS (Fringe Field Switching) type . . . etc.
VA type thin film transistor display is used to the large size panel, for example, liquid crystal TV . . . etc., because of the high aperture ratio, the high resolution, the wide viewing angle . . . etc. But in the small size and high resolution panel, the traditional designed pixel of crystal panel, the VA type thin film transistor display is not widespread.
Referring to FIG. 1 and FIG. 2 demonstrates the main operating principle. FIG. 1 illustrates the current pixel structure of VA type display. FIG. 2 is the A-A cross section view of FIG. 1. The upper substrate is the common electrode substrate, and the down substrate is the pixel electrode arranged on the substrate, and the pixel electrode layout is made on the ITO substrate. To achieve the purpose of display, the curved edge electric field is formed by the different electrode pattern of the upper substrate and the down substrate at the edge of the pixel, and the edge electric field controls the liquid crystal direction of the panel. Comparing to the traditional MVA type, this kind of technology reduces the expensive process of protrusion structure, and has very high contrast and viewing angle symmetry.
The Problem of the Pixel Structure:
The crossover shape of the ITO common electrode between the pixel electrodes is patterned from the same ITO layer. Because of the limitation of the process, the width between the pixel electrode and the common electrode, and the width of the common electrode itself must keep the same width. The width brings the dark line from the pixels, and reduces the liquid crystal performance and transmittance.
The pixel electrode and the common electrode in the same ITO layer and the same pixel easily have the short-circuited problem and the defect of the display.
The through via is added at the external of the pixel to connect the common electrode and the external common electrode wire.